The present invention relates generally to the field of packaged electrical systems, such as for the distribution of power signals to controlled equipment. More particularly, the invention relates to a bus support system for electrical enclosures that can accommodate busses for four-wire three-phase systems and three-wire three-phase systems.
Electrical enclosures for use with power electronic equipment and switch gear are known and have been used for many years. In industrial applications, for example, such switch gear, as well as semi-conductor power electronic circuits, programmable logic controllers, motor controllers, and so forth, are often housed in large electrical enclosures. The enclosures are often divided into separate compartments or segments in which related equipment and circuits may be disposed. Access to the components may be had through a door, with separate doors typically being provided for separate compartments in large enclosures. Enclosures of this type are currently in use in systems commonly known as motor control centers (MCCs).
Such systems are configured in different ways for different markets, particularly in international markets. For example, in certain markets the systems may accommodate three-wire three-phase power, while in others the systems are designed for four-wire three-phase power. In general, all three-phase power systems carry power over three conductors in sinusoidal waveforms that are offset from one another by 120° of phase difference. Four-wire systems add a fourth neutral conductor to the three power conductors. Such configurations may respond to requirements of local electrical codes, national or regional power grids or systems, customs, and so forth.
Manufacturers of such electrical systems must generally accommodate both three-wire and four-wire three-phase power configurations. The need to provide for power busses for the three power phases, along with a fourth power bus for a neutral conductor can, however, add to either the cost of all systems or to the number of different systems that must be manufactured, assembled and stocked by the system providers. That is, if a universal system is equipped for four-wire three-phase power, additional cost is built into the systems where only three-wire three-phase power is needed by the customer. Conversely, systems built only for three-wire three-phase power are simply unsuitable for use where four-wire three-phase power is required.
There is a need, therefore, for improved electrical system configurations that can accommodate both three-wire three-phase power and four-wire three-phase power. There is a particular need for a system that can be easily and economically configured for different markets based upon a single physical standard.